One of the major age-related damaging agents are reactive oxygen species (ROS). The brain is more vulnerable to oxidative stress than other organs as concomitant low activity and capacity of antioxidative protection systems allow for increased exposure of target molecules to ROS. Since neurons are postmitotic cells, they have to live with cellular damage accumulated over many decades. Increased levels of ROS (also termed "oxidative stress"), produced by normal mitochondrial activity, inflammation and excess glutamate levels, are proposed to accelerate neurodegenerative processes characteristic of Alzheimer's disease. This review presents evidence of the importance of oxidative stress in the pathogenesis of these diseases and explains the nature of different types of ROS mediating neuronal damage. Furthermore, the potential beneficial effects of neuroprotective treatments, including antioxidants and anti - glutamatergic drugs are discussed.